mac80211: remove bogus rcu_read_lock()

Another remnant of the previous key locking scheme
needs to be removed -- this causes a warning
otherwise as ieee80211_set_default_mgmt_key will
acquire a mutex.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/cfg.c

@@ -324,15 +324,10 @@ static int ieee80211_config_default_mgmt_key(struct wiphy *wiphy,
 					     struct net_device *dev,
 					     u8 key_idx)
 {
-	struct ieee80211_sub_if_data *sdata;
-
-	rcu_read_lock();
+	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 
-	sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 	ieee80211_set_default_mgmt_key(sdata, key_idx);
 
-	rcu_read_unlock();
-
 	return 0;
 }